Integrated Propulsion and Steering System

ABSTRACT

An electrically driven propulsion system for a watercraft comprises an electric motor, a pulse inverter, a thrust bearing, and a transmission is presented. The pulse inverter can be electrically coupled to the electric motor and adapted to provide an electrical supply power of at least 50 kW to the electric motor. The electrically driven propulsion system further comprises a common waterproof housing. An external section of the transmission can be arranged outside of the common waterproof housing. The transmission can be adapted to rotationally couple the external section of the transmission to the electric motor. The thrust bearing can be mechanically coupled to the rotary shaft of said transmission and to the common waterproof housing. The thrust bearing can be adapted to transfer a force applied to the transmission along an axial direction of said rotary shaft of the transmission to the common waterproof housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of European PatentApplication No. 22153993.5, filed Jan. 28, 2022, the entirety of whichis herein incorporated by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates to a propulsion system for a watercraft,and more specifically to an electrically driven propulsion system, inparticular to an integrated propulsion system.

BACKGROUND

A conventional propulsion system for motorized watercraft is based on anengine, such as a diesel or gasoline combustion engine, which may bearranged inboard or outboard. Sometimes, a replacement of a component ofthe propulsion system, in particular of the motor, is desirable, forexample to upgrade the system with a more silent and sustainableelectric drive instead of the combustion engine, or because of a defect.

An inboard engine is overall well-protected by the hull fromenvironmental influences such as seawater, weather conditions, damage inaccidents, vandalism or theft. However, if the inboard engine fails, themotorized watercraft will typically need to visit a port or a shipyardfor diagnostics of the failure and a subsequent repair or exchange ofengine parts. In pleasure vessels such failures usually occur at randomand are rarely detected ahead of time. Often the vessel needs to becraned out of the water and stored on land. Depending on the type offailure and the availability of replacement parts, this process may takeseveral days or even longer.

In case of a failure of an outboard engine, diagnostics of the failureand a subsequent repair or exchange of engine parts in a harbor or ashipyard are also an option. The exposed arrangement of the outboardmotor alternatively permits to change the engine as a whole quickly, ifa replacement part is available. However, the exposed arrangementresults in a stronger exposure to the environmental influences.Moreover, the exposed arrangement of the outboard engine may cause asignificant noise level onboard and especially on deck. Also, in case ofa high-power outboard engine, for example with a power of 50 kW andmore, changing the engine as a whole may be complicated by itssignificant weight, for example in case of a diesel engine.

SUMMARY

The present disclosure provides for an improved propulsion system for awatercraft which facilitates installation and replacement.

On a conventional vessel, the propulsion system may be composed ofindividually selected, separate components, which a plethora ofcombinations on different boats. Consequently, installation, replacementand repair may require expert knowledge of each individual component.

In a first aspect, an electrically driven propulsion system for awatercraft comprises an electric motor adapted to provide a mechanicalpower of at least 50 kW, a pulse inverter, a thrust bearing, and atransmission. The pulse inverter is electrically coupled to the electricmotor and adapted to provide an electrical supply power of at least 50kW to the electric motor. The transmission comprises a rotary shaft. Theelectrically driven propulsion system further comprises a commonwaterproof housing. The electric motor, the pulse inverter and anenclosed section of the transmission are arranged inside the commonwaterproof housing. An external section of the transmission is arrangedoutside of the common waterproof housing. The transmission is adapted torotationally couple the external section of the transmission to theelectric motor. The thrust bearing is mechanically coupled to the rotaryshaft of said transmission and to the common waterproof housing. Thethrust bearing is adapted to transfer a force applied to thetransmission along an axial direction of said rotary shaft of thetransmission to the common waterproof housing.

The electrically driven propulsion system may serve to combine allessential electrical and electromechanical components in an integrated,monolithic unit defined by the common waterproof housing. Therefore, auser equipping the watercraft with the electrically driven propulsionsystem may implement a fully optimized system, without any need formodifications at the user's end. No expert skill of the user isrequired, as may be the case for conventional systems combiningindividually selected components. A risk of implementing a suboptimalsystem, for example related to a suboptimal combination of pulseinverter and electric motor, may be avoided.

Making use of an electric motor instead of a conventional combustionengine, the electrically driven propulsion system may improve thesustainability of the watercraft as well as the comfort on board.Vibrations and noise may be minimized using the electric motor. As itcombines all essential components in a single component, theelectrically driven propulsion system according to the invention may beideal for replacing a conventional combustion engine, avoiding an effortof designing an individual electrical system for the boat.

Moreover, the electrically driven propulsion system may be replaced as awhole quickly, in particular in case of a failure of one of itscomponents. The defective component may be diagnosed and replaced lateroff-site, for example in a dedicated facility, as the watercraft withthe replaced propulsion system is already back in operation. In otherwords, the electrically driven propulsion system according to thedescription may be supplied to the user as a plug-n-play system, whichmay be installed and replaced quickly and easily.

Moreover, the electric motor may have a lower weight than a combustionengine adapted to provide a similar mechanical power, thus facilitatingthe installation or replacement of the electrically driven propulsionsystem.

The common waterproof housing may improve the electrical safety of thesystem and reduce a risk of an electric shock for a user. Water may beprevented from entering the electrical components and corroding them orcausing unwanted shunts, which might otherwise pose a danger to theuser.

The common waterproof housing may be composed of an electricallyinsulating material or comprise a layer of an electrically insulatingmaterial. The layer of the electrically conductive material may fullysurround the electric motor and/or a motor inverter and/or anyelectrical connection between the electric motor, the inverter and/or apower inlet.

Alternatively, or in addition, the common waterproof housing maycomprise a layer of an electrically conductive material, wherein thelayer of the electrically conductive material fully surrounds theelectric motor and/or the motor inverter and/or any electricalconnection between the electric motor, the inverter and/or the powerinlet. The layer of the electrically conductive material may begrounded.

The axial direction of the rotary shaft may refer to an axis of rotationthe rotary shaft.

Alternatively, or in addition, the axial direction of the rotary shaftmay refer to a thrust direction of the rotary shaft through the commonwaterproof housing.

The axial direction of the rotary shaft may refer to an axis of rotationof a rotary shaft thrusting through the common waterproof housing.

The axial direction of the rotary shaft may refer to a direction alongwhich the rotary shaft extends.

The axial direction of the rotary shaft may refer to a line connectingthe enclosed section of the transmission and the external section of thetransmission, in particular to a line connecting a portion the enclosedsection of the transmission closest to the external section and aportion of the external section of the transmission closest to theenclosed section.

The external section of the transmission may comprise a propellercoupling adapted for mounting a propeller.

Corresponding embodiments may comprise all essential electrical,electromechanical, and mechanical components for driving the propellerof the watercraft using the electric motor. The additional integrationof the mechanical components may further facilitate a simpleinstallation of a fully optimized system.

The watercraft may comprise a hull.

The hull may comprise an opening.

The electrically driven propulsion system may be adapted to be connectedas a whole to the hull with the opening, such that at least a section ofthe electric motor is arranged on a first side of the opening and thepropeller coupling and at least a portion of the common waterproofhousing are arranged on a second side of the opening opposite to thefirst side, and such that a waterproof connection forms between thecommon waterproof housing and the hull.

When the electrically driven propulsion is connected to a hull, theelectric motors may be located inside of the hull where they areprotected from environmental influences and acoustically shielded tominimize a noise level on board and on deck.

The arrangement of the electrically driven propulsion system in the hullor transom, part inboard and part outboard, may further allow for alinear arrangement of the system, thus avoiding additional mechanisms toconvert a vertical rotation into a rotation around a horizontal axis orvice versa. In particular, a known planetary gearing may be incorporatedinto the enclosed section of the transmission to optimize its optimumrotational speed (i. e., the rotational speed of the external sectionfor which the overall efficiency of electrically driven propulsionsystem is the highest) to a given watercraft or propeller.

This arrangement further may further allow for incorporating a gearingmechanism (gear box) in the electrically driven propulsion system toprovide a system with a maximized efficiency at a rotational speedmatched to an optimum rotation speed of a propeller for accelerating thewatercraft.

The electrically driven propulsion system may be adapted to be connectedas a whole to the hull with the opening, such that the electric motor isarranged on the first side of the opening and/or such that at least aportion of the motor section is arranged on the first side of theopening, in particular the entire motor section.

The hull may comprise a transom. The opening may be arranged on thetransom.

Alternatively, the opening may be arranged on a bottom side of the hull.

The propeller coupling may comprise a threading, a hub and/or a drivingcollar adapted for mounting a propeller.

The electrically driven propulsion system may be adapted to be connectedas a whole to the watercraft, in particular to the hull with theopening, for example such that at least a portion of the enclosedsection of the transmission is arranged on the second side of theopening.

The waterproof connection may be adapted to close the opening of thehull, in particular in a waterproof way.

The first side may correspond to an inside of the watercraft. The secondside may correspond to an outside of the watercraft.

The electrically driven propulsion system may be adapted to be connectedas a whole to the hull with the opening from the outside of thewatercraft.

The transmission may be adapted to rotationally couple the propellercoupling to the electric motor and/or comprise any element adapted torotationally couple the propeller coupling to the electric motor.

The transmission may comprise a gear ratio. The gear ratio may beselected according to the watercraft and mounting type within the craft.

The electrically driven propulsion system may be adapted to be mountedto a connecting frame connected to the hull with the opening. Theconnecting frame may be arranged between the hull with the opening andthe electrically driven propulsion system.

The electrically driven propulsion system may further comprise anoise/vibration sensor arranged inside the common waterproof housing, inparticular a plurality of noise/vibration sensors arranged inside thecommon waterproof housing.

The noise/vibration sensor may be adapted to generate an electronicsignal corresponding to a sound or vibrational level at thenoise/vibration sensor.

The noise/vibration sensor may be adapted to detect a change in a soundor vibrational level of the electrically driven propulsion system, inparticular an increase in the sound or vibrational level of theelectrically driven propulsion system, in particular of the electricmotor and/or of the transmission.

The noise/vibration sensor may comprise a signal line extending frominside of the common waterproof housing out of the common waterproofhousing. The signal line of the noise/vibration sensor may comprise awaterproof feedthrough through the common waterproof housing. The signalline may be adapted to transfer the electronic signal from inside of thecommon waterproof housing out of the common waterproof housing.

The electrically driven propulsion system may further comprise aprocessor for analyzing the electronic signal of the noise/vibrationsensor.

The detected changes in the sound, noise or vibrational pattern of theelectrically driven propulsion system or its components may serve as anindication of an upcoming failure of the system. The noise/vibrationsensor may generate electronic signals representing the detected soundlevel, and send these electronic signals through a signal line foranalysis by a processor to detect a change in the noise patterncharacteristic of a failure. The processor may be part of theelectrically driven propulsion system or the noise/vibration sensor.

Alternative, or in addition, the signal line may transmit the electronicsignal out of the common waterproof housing for analysis by an externalprocessor. When the processor detects the change, an electronic reportmessage recommending an exchange of the electrically driven propulsionsystem may be generated.

The noise/vibration sensor may be adapted to detect a contact or acollision of the electrically driven propulsion system or the hull withan obstacle. In particular, the noise/vibration sensor may be adapted todetect a change in the sound or vibrational level exceeding a criticalvalue, in particular a critical value related to a collision of theelectrically driven propulsion system or the hull with an obstacle. Thenoise/vibration sensor or a processor coupled to the noise/vibrationsensor may be adapted to send an electronic warning message upondetection of a contact or a collision.

The noise/vibration sensor may be arranged in a vicinity of the electricmotor, in particular in direct physical contact with the electric motor.

Alternatively or in addition, the noise/vibration sensor may be arrangedin a vicinity of the portion of the common waterproof housing arrangedon the second side, in particular in the portion of the commonwaterproof housing arranged on the second side and/or in direct contactwith an inner side of the portion of the common waterproof housingarranged on the second side.

The electric motor may be an axial flux motor.

A geometry of the axial flux motor may beneficially permit to add orremove an electric motor, and may thereby improve the modular design andthe design flexibility of the electrically driven propulsion system. Theaxial flux motor may be constructed with higher power densities thanconventional engines and electric motors, such as radial flux motors. Asa revolution speed of the axial flux motor is similar to the optimalrevolution speed of the propeller coupling or the propeller, thetransmission may have a small gear ratio and thus a higher efficiencythan a gearbox with a high gear ratio typically applied in combinationwith an engine or an electric motor with a higher revolution speed.

The transmission may comprise a first rotary shaft functionally coupledto the electric motor.

The transmission may comprise a second rotary shaft comprising theexternal section of the transmission, in particular the propellercoupling.

The transmission may comprise a gear ratio.

The transmission may comprise a gearing mechanism. The gearing mechanismmay be adapted to comprise the gear ratio. The gearing mechanism may beadapted to rotationally couple the first rotary shaft to the secondrotary shaft.

The gearing mechanism may be adapted to implement an offset between anaxis of the first rotary shaft and an axis of the second rotary shaft.

Alternatively, the transmission may comprise a belt or a chainrotationally coupling the first rotary shaft and the second rotaryshaft.

The belt or the chain may be adapted to implement an offset between anaxis of the first rotary shaft and an axis of the second rotary shaft.

The gearing mechanism may comprise a spur gear adapted to implement theoffset between the axis of the first rotary shaft and the axis of thesecond rotary shaft.

The gear ratio may refer to a revolution speed of the first rotary shaftper revolution speed of the second rotary shaft.

The spur gear may be adapted to implement the gear ratio.

Alternatively, or in addition, the gearing mechanism may comprise aplanetary gearing. The planetary gearing or a combination of theplanetary gearing with the spur gear may be adapted to implement thegear ratio.

The gear ratio of the gearing mechanism may be at most 2, in particularat most 1.5 in particular at most 1.3 or at most 1.25.

A small gear ratio may improve the efficiency of the transmission and ofthe electrically driven propulsion system, for example as compared to ahigh gear ratio typically applied in combination with an engine or anelectric motor with a higher revolution speed.

The thrust bearing may be adapted to implement a waterproof feedthroughof the transmission through the common waterproof housing.

The thrust bearing may be rotationally coupled to a rotary shaft of thetransmission, in particular to the second rotary shaft.

The thrust bearing may be rotationally coupled to the gearing mechanism.

The thrust bearing may form a section of the common waterproof housingor at least a section of the thrust bearing may be arranged in thecommon waterproof housing.

The thrust bearing may provide a waterproof connection between thetransmission, in particular the rotary shaft, and the common waterproofhousing.

The thrust bearing may comprise a first ring coupled to the rotary shaftand a second ring coupled to the common waterproof housing. The firstring and the second ring may be arranged on or around an axis of therotary shaft at different positions along the axial direction.

The first ring may be arranged abaft at least a section of the secondring, in particular abaft the entire second ring.

The first ring and the second ring may be separated by roller elements,in particular only by the roller elements.

The electrically driven propulsion system may be adapted to rotate thepropeller to generate the force applied to the transmission along theaxial direction of the transmission.

The gear ratio may be selected for a revolution speed of the firstrotary shaft to be at least 1700 revolutions per minute (rpm) when theelectromotor is operated at a motor revolution speed adapted for amaximum efficiency of the electromotor.

The gear ratio may be selected for the revolution speed of the firstrotary shaft to be at most 2500 revolutions per minute (rpm) when theelectromotor is operated at the motor revolution speed adapted for themaximum efficiency of the electromotor.

The revolution speed of the first rotary shaft, or of the propellercoupling, or of the propeller, respectively, in the range of 1700-2500rpm, may ensure a maximum efficiency of the propulsion system. Inparticular, a smaller revolution speed closer to 1700 rpm may beselected for a propulsion system for a larger watercraft, and a largerrevolution speed closer to 2500 rpm may be selected for a propulsionsystem for a smaller watercraft.

The second rotary shaft may be displaced with respect to the firstrotary shaft in the plane perpendicular to the longitudinal direction.

The second rotary shaft may be essentially parallel to the first rotaryshaft, for example within an angle of 10° or within an angle of 8°.

The transmission may comprise a propeller shaft (second rotary shaft)comprising the propeller coupling and an axis, and an orientation of theaxis of the second rotary shaft may be static.

A static second rotary shaft (propeller shaft) may improve therobustness and durability of the system and reduce a risk of a failure.

The electrically driven propulsion system may further comprise apropeller mounted to the propeller coupling.

The propeller may be a propeller for a surface drive.

A corresponding propeller may optimize the electrically drivenpropulsion system for an application as a surface drive. A surface drivemay provide an improved energy efficiency as compared to a conventionaldrive, in particular at an elevated speed such as at least 20 knots.

The propeller may comprise a radial section, wherein the radial sectionextends radially from a center of the propeller.

The propeller may comprise an essentially flat section in directphysical contact with the radial section. The essentially flat sectionmay extend from the radial section essentially along an azimuthaldirection.

The essentially flat section may comprise an outer edge.

The outer edge may be essentially perpendicular to the radial section ina stern projection of the electrically driven propulsion system.

The transmission may be adapted to rotationally couple the propeller tothe electric motor and/or comprise any element adapted to rotationallycouple the propeller to the electric motor.

The propeller may comprise a diameter of at least 20 cm, in particularat least 25 cm, in particular at least 30 cm, in particular at least 35cm or at least 40 cm.

The propeller may comprise a diameter of at most 70 cm, in particular atmost 60 cm or at most 55 cm.

The propeller may comprise a pitch of at least 40 cm, in particular atleast 45 cm, in particular at least 50 cm, or at least 55 cm.

The propeller may comprise a pitch of at most 110 cm, in particular atmost 100 cm, in particular at most 90 cm, or at most 85 cm.

A ratio of the diameter of the propeller over the pitch of the propellermay be at least 1.2, in particular at least 1.3 or at least 1.4.

A ratio of the diameter of the propeller over the pitch of the propellermay be at most 1.8, in particular at most 1.7 or at most 1.6.

The pitch may be defined by angle of the outer edge with respect to alongitudinal direction. A tangent of the angle of the outer edge withrespect to a longitudinal direction may be the diameter of the propellerper half the pitch of the propeller.

A weight of the electrically driven propulsion system per maximum powerof the electric motor may not exceed 0.7 kg/kW, in particular not exceed0.6 kg/kW, in particular not exceed 0.5 kg/kW, in particular not exceed0.4 kg/kW or not exceed 0.3 kg/kW.

A weight of the electrically driven propulsion system per maximum torqueat the propeller may not exceed 0.14 kg/Nm, in particular not exceed0.12 kg/Nm, in particular not exceed 0.1 kg/Nm, in particular not exceed0.08 kg/Nm or not exceed 0.06 kg/Nm.

In the context of the present disclosure, a waterproof housing may beunderstood to denote a housing at least a portion of which is protectedagainst liquid ingress.

In particular, the waterproof housing may be a housing at least aportion of which is protected at least against spraying water, and/orprotected at least against splashing of water, and/or protected at leastagainst water jets, and/or protected at least against immersion.

In the context of the present disclosure, the level of ingressprotection may be quantified in terms of the ingress protection code (IPcode) defined by the International Electrotechnical Commission (IEC).For instance, the waterproof housing may have IP code IPxy or higher,wherein x=3, . . . , 6 denotes the level of protection against solidparticles and y=3, . . . , 6 denotes the level of protection againstliquid ingress. In particular, y may be at least 4, or at least 5.

The common waterproof housing may be adapted to fulfill at least IP65standards.

In an embodiment, different portions of the housing may have differentlevels of protection against liquid ingress.

The waterproof connection between the common waterproof housing and thehull may encircle the opening.

The common waterproof housing may comprise a motor section in which theelectric motor is arranged.

The common waterproof housing may comprise a transmission section inwhich the enclosed section of the transmission is arranged. Thetransmission section may be different from the motor section.

The motor section may completely be arranged forward of the portion ofthe common waterproof housing arranged on the second side transmissionsection and/or of the transmission section. In particular, the motorsection may fully be comprised in a volume defined by a forwardtranslation of a cross section of the portion of the common waterproofhousing arranged on the second side transmission section and/or a crosssection of the transmission section.

Corresponding embodiments may provide an optimized geometry for mountingthem to a transom of the watercraft. Therefore, the motor section may beintroduced into the transom at least partially, preferably as a whole,such that the motor rests inside the hull. The portion of the commonwaterproof housing arranged on the second side transmission sectionand/or of the transmission section may be wider than the motor sectionand may serve as a stopper to ensure the predefined mounting depth. Itmay end up position abaft the motor section and the motor, at an idealposition e. g. for a surface drive.

The transmission section may be arranged abaft the motor section and/orbelow the motor section, for example on average, according to therespective centers of the sections, or completely.

The electrically driven propulsion system may comprise a longitudinaldirection.

The longitudinal direction of the electrically driven propulsion systemmay refer to a direction perpendicular to the hull at the opening.

The transmission of the electrically driven propulsion system may beadapted to pass through the opening of the hull when the electricallydriven propulsion system is connected to the hull.

The longitudinal direction of the transmission may refer to a directionat which the transmission passes through the opening of the hull.

An extension of the portion of the common waterproof housing arranged onthe second side in a plane perpendicular to the longitudinal directionmay exceed an extension of the motor section in a second planeperpendicular to the longitudinal direction.

An extension of the transmission section in a plane perpendicular to thelongitudinal direction may exceed an extension of the motor section in asecond plane perpendicular to the longitudinal direction.

A width of the portion of the common waterproof housing adapted to bearranged on the second side may exceed a width of the motor section.

This arrangement may support a quick and simple exchange of theelectrically driven propulsion system to the ideal mounting depth byinserting the motor section into the hull and using the portion of thecommon waterproof housing adapted to be arranged on the second side as astopper.

The width of the portion of the common waterproof housing adapted to bearranged on the second side may refer to a width of a cross section ofthe portion of the common waterproof housing arranged on the secondside.

The width of the motor section may refer to a width of a cross sectionof the motor section.

The extension of the transmission section in the plane perpendicular tothe longitudinal direction may refer to a width of the transmissionsection or to a height of the transmission section or to a maximumextension of the transmission section in the plane perpendicular to thelongitudinal direction. For example, the extension of the transmissionsection in the plane perpendicular to the longitudinal direction mayrefer to a width or a height of the transmission section, whichever oneis larger.

The extension of the motor section in the second plane perpendicular tothe longitudinal direction may refer to a width of the motor section orto a height of the motor section or to a maximum extension of the motorsection in the second plane perpendicular to the longitudinal direction.For example, the extension of the motor section in the second planeperpendicular to the longitudinal direction may refer to a width or aheight of the motor section, whichever one is larger.

The extension of the motor section along any direction in the planeperpendicular to the longitudinal direction may be at most 80 cm, inparticular at most 70 cm, or at most 60 cm.

The extension of the motor section along any direction in the planeperpendicular to the longitudinal direction may be at least 20 cm, inparticular at least 25 cm, or at least 30 cm.

The motor section may be adapted to provide a motor upgrade spaceadapted to receive a motor power upgrade component.

The motor power upgrade component may be adapted to increase themechanical power that the electric motor is adapted to provide. Inparticular, the motor power upgrade component may be adapted to increasethe mechanical power that the electric motor is adapted to provide by atleast 20 kW, in particular by at least 30 kW, in particular by at least40 kW or by at least 50 kW.

The motor upgrade space may be arranged in direct contact with thetransmission, in particular with the enclosed section of thetransmission and/or the first rotary shaft.

A corresponding electric motor and the corresponding motor section mayfacilitate a modular design of the electrically driven propulsionsystem. The electrically driven propulsion system may easily be adaptedto fulfill the requirements of a wide variety of ships or boats, forexample in terms of propulsion power. Moreover, an electrically drivenpropulsion system held in readiness for repair may quickly be adapted toreplace any other specimen of the electrically driven propulsion systemin case of a failure.

The motor upgrade space may be comprised in the electric motor, and/orthe electric motor may be adapted to receive the motor power upgradecomponent.

The motor upgrade space may be arranged in the electric motor or indirect physical contact with the electric motor.

The electric motor may comprise at least one stator adapted to generatean electric field in a field region, and at least one rotor arrangedrotatably in the field region. The motor upgrade space may be arrangedin the field region. The motor power upgrade component may comprise orbe at least one additional rotor adapted to be arranged rotatably in thefield region.

The at least one rotor and the motor upgrade space and/or the at leastone additional rotor may have a same shape, in particular a samecylindrical shape.

The at least one additional rotor may comprise or be at least oneadditional rotor disc.

The at least one rotor and the at least one additional rotor may have asame input voltage or a same input current.

The at least one additional rotor may be adapted to generate a secondmagnetic field. The at least one stator may comprise or be composed of afirst stator and a second stator, and the motor upgrade space may bearranged between the first stator and the second stator.

Alternatively, the motor upgrade space and the at least one additionalrotor may be arranged on opposite sides of the at least one stator.

Alternatively, or in addition, the motor power upgrade component maycomprise or be at least one additional electric motor exchangeable withthe electric motor, in particular at least two additional electricmotors each exchangeable with the electric motor, in particular at leastthree additional electric motors each exchangeable with the electricmotor.

The electric motor and the motor upgrade space and/or the additionalelectric motor exchangeable with the electric motor may have a sameshape, in particular a same cylindrical shape.

The electric motor and the motor upgrade space and/or the additionalelectric motor exchangeable with the electric motor may have a sameradius or a same extension along a radial direction of the respectiveelectric motor. Alternatively, or in addition, the electric motor andthe additional electric motor exchangeable with the electric motor mayhave a same length or a same extension along a longitudinal direction ofthe respective electric motor.

The electric motor and the additional electric motor exchangeable withthe electric motor may have a same input voltage or a same inputcurrent.

The electric motor and the additional electric motor exchangeable withthe electric motor may have a same maximum power.

All electric motors arranged in the common waterproof housing and/or theelectric motor with the motor power upgrade component may together beadapted to provide a total mechanical power of at least 100 kW, inparticular of at least 300 kW, in particular of at least 400 kW or of atleast 500 kW.

The motor upgrade space may be arranged abaft the electric motor or thestator, or forward of the electric motor or the stator, in particular indirect physical contact.

The transmission may be adapted to transfer a mechanical power of atleast 100 kW from the electric motor to the external section, inparticular to the propeller coupling, in particular a mechanical powerof at least 150 kW, in particular of at least 200 kW, in particular ofat least 300 kW, in particular of at least 400 kW or of at least 500 kW.

Additional components, such as the transmission or a pulse inverter, maybe predesigned to support the motor upgrade with the motor power upgradecomponent.

The common waterproof housing may comprise a ring-shaped seal faceadapted to provide the waterproof connection.

The ring-shaped seal face may be adapted to encircle the opening of thehull.

The ring-shaped seal face may encircle the transmission, in particularthe first rotary shaft or the second rotary shaft and/or a gearbox ofthe transmission.

The ring-shaped seal face may encircle a region comprising a projectionof the motor section onto the region.

The longitudinal direction may refer to a direction perpendicular to thering-shaped seal face.

The transmission may pass through the ring-shaped seal face.

The longitudinal direction may refer to a direction at which thetransmission passes through the ring-shaped seal face.

The electrically driven propulsion system may comprise fixing means indirect physical contact with the ring-shaped seal face and adapted toprovide the waterproof connection.

The fixing means of the electrically driven propulsion system may beadapted to couple to through holes of the hull with the opening or in aconnecting frame.

The fixing means of the electrically driven propulsion system maycomprise or be threaded holes and/or threaded studs.

The ring-shaped seal face may be adapted to be arranged on the secondside of the opening.

The electrically driven propulsion system may further comprise a heatexchanger arranged in the common waterproof housing.

A primary side of the heat exchanger may comprise at least one primarycoolant opening.

The at least one primary coolant opening may be arranged outside of thecommon waterproof housing.

In particular, the at least one primary coolant opening may be adaptedto be arranged on the second side of the opening.

A secondary side of the heat exchanger may comprise at least onesecondary coolant opening arranged outside of the common waterproofhousing.

In particular, the at least one primary coolant opening may be adaptedto be arranged on the first side of the opening.

The heat exchanger may be adapted to transfer heat from its secondaryside to its primary side, in particular from a coolant of the secondaryside to a coolant of the primary side.

The heat exchanger may comprise a coolant pump adapted to generate aflow of the coolant of the primary side of the heat exchanger and/or thesecondary side of the heat exchanger.

The primary side of the heat exchanger may be adapted to receive and/orto release water from the second side of the opening, in particular(sea) water from the second side of the opening. In particular, the atleast one primary coolant opening may be adapted to be below a waterline of the watercraft when the electrically driven propulsion system ismounted to the watercraft.

The primary side of the heat exchanger may be adapted to use water takenup from the surrounding body of water via the at least one primarycoolant opening as a coolant, in particular for cooling the secondaryside of the heat exchanger.

The secondary side of the heat exchanger may comprise a cooling liquidof a selected composition and or a cooling liquid such as glycol.

The secondary side of the heat exchanger may be thermally coupled to atleast one element of the electrically driven propulsion system such asthe electric motor and/or the pulse inverter and/or the thrust bearing.

The secondary side of the heat exchanger, may comprise at least onesecondary coolant channel thermally coupling the heat exchanger to theat least one element of the electrically driven propulsion system suchas the electric motor and/or the pulse inverter and/or the thrustbearing and/or to the at least one secondary coolant opening.

The primary side of the heat exchanger may comprise at least one primarycoolant channel thermally coupling the heat exchanger to the at leastone primary coolant opening.

The electrically driven propulsion system may comprise an integratedheat exchanger for cooling the mechanical or electrical components ofthe system, such as the electric motor or the pulse inverter. Theintegration of the heat exchanger with the system may give direct accessto a surrounding body of water, which may supply the coolant for theprimary side of the heat exchanger, without requiring any furtheropenings in the hull.

When the electrically driven propulsion system is mounted to awatercraft, the secondary coolant opening may be used to access thesecondary side of the heat exchanger from inside of the watercraft anduse it for cooling watercraft facilities such as a battery, additionalelectronics, or a cabin.

The at least one primary coolant opening and the at least one secondarycoolant opening may refer to openings for a coolant in the commonwaterproof housing connecting to the heat exchanger and waterproof toany other component of the electrically driven propulsion system. Thepulse inverter may comprise a power inlet functionally accessible fromoutside the common waterproof housing. The power inlet may be adapted tobe arranged on the first side of the opening.

The pulse inverter may be adapted to provide an electrical output powerof at least two times the mechanical power that the electric motor isadapted to provide, in particular of at least three times the mechanicalpower that the electric motor is adapted to provide or at least fourtimes the mechanical power that the electric motor is adapted toprovide.

The pulse inverter may be adapted to provide an electrical output powerof at least 100 kW, in particular of at least 150 kW, in particular ofat least 200 kW, in particular of at least 300 kW, in particular of atleast 400 kW or of at least 500 kW.

As the pulse inverter is arranged in the common waterproof housingtogether with the electric motors, an optimized pulse inverter for theelectric motors may be provided, for example to optimize an energyefficiency of the combination of pulse inverter and electric motors,thus optimizing a range of a watercraft using the electrically drivenpropulsion system.

The pulse inverter may be adapted to be coupled to the at least oneadditional electric motor and to provide an electrical supply current tothe at least one additional electric motor. The pulse inverter may beadapted to be coupled to the at least two additional electric motors andto provide an electrical supply current to the at least two additionalelectric motors. The pulse inverter may be adapted to be coupled to theat least three additional electric motors and to provide an electricalsupply current to the at least three additional electric motors.

The pulse inverter may comprise a pulse width modulator.

The electrically driven propulsion system may further comprise a rudderactuator, wherein at least a section of the rudder actuator is arrangedinside the common waterproof housing, in particular wherein the entirerudder actuator is arranged inside the common waterproof housing.

The rudder actuator may comprise an electric input. The electric inputmay be functionally accessible from outside the common waterproofhousing.

The rudder actuator may be adapted to convert the electric input into amechanical movement.

The rudder actuator may further comprise a tiller arm adapted to coupleto at least one rudder.

In particular, the tiller arm may be adapted to transmit the mechanicalmovement to the at least one rudder.

The tiller arm may be adapted to couple to at least two rudders, inparticular to exactly two rudders.

The rudder actuator may comprise a central tiller arm adapted to coupleto a starboard rudder and a portside rudder. The central tiller arm maybe adapted to couple to the starboard rudder via a starboard tiller arm.The central tiller arm may be adapted to couple to the portside ruddervia a portside tiller arm.

The electrically driven propulsion system may further comprise at leastone rudder, in particular at least two rudders, in particular exactlytwo rudders.

The at least one rudder may be arranged portside and/or starboard thepropeller coupling.

The electrically driven propulsion system may further comprise a datainput functionally accessible from outside the common waterproof housingand coupled to the pulse inverter and/or the rudder actuator, inparticular wherein the data input comprises a data input connectorfunctionally accessible from outside the common waterproof housing andadapted to be arranged on the first side of the opening.

The data input may be adapted to control an output power of the pulseinverter and/or a position of a rudder.

The data input may allow for software updates of the electrically drivenpropulsion system, in particular to improve the energy efficiency of theelectric motor, the transmission, and/or the pulse inverter evenfurther.

The data input may be adapted to receive at least one controllerparameter for the pulse inverter and/or the rudder actuator, and toupdate the electrically driven propulsion system with the at least onecontroller parameter.

The electrically driven propulsion system may further comprise a batteryadapted to provide a supply power of at least 50 kW to the pulseinverter. The battery may be arranged outside of the common waterproofhousing and be adapted to provide the supply power to the pulse invertervia the power inlet.

The battery may comprise a battery voltage matching an optimum inputvoltage of the pulse inverter. The optimum input voltage of the pulseinverter may correspond to an input voltage of the pulse inverter, atwhich a ratio between an output power of the pulse inverter and thesupply power provided to the pulse inverter is maximum.

In a second aspect, a connecting frame for connecting a propulsionsystem to a hull with an opening comprises a first ring-shaped element,a second ring-shaped element, a first sealing face, and a second sealingface. The first ring-shaped element comprises a first opening, firstconnecting elements, and through holes. The second ring-shaped elementcomprises a second opening; second connecting elements, wherein thefirst connecting elements and the second connecting elements comprise afirst common arrangement; and detachable connection elements adapted tocouple to the fixing means of the propulsion system. The first sealingface is arranged on the first ring-shaped element and encircles thefirst opening. The second seal face is arranged on the first ring-shapedelement opposite to the first sealing face and encircling the secondopening. The first ring-shaped element and second ring-shaped elementare adapted to be connected using the first connecting elements and thesecond connecting elements and with a relative orientation defined bythe first common arrangement. According to the relative orientation, thefirst opening overlaps with the second opening to form an opening of theconnecting frame; the through holes coincide with the detachableconnection elements; and the first sealing face is arranged between theconnected first ring-shaped element and second ring-shaped element andadapted to provide a waterproof connection between the connecting frameand the hull with the opening.

The connecting frame may allow for a quick and safe exchange of theelectrically driven propulsion system as a whole. In particular, therisk of damaging the hull is reduced, as any physical contact betweenmoving components and the hull may be prevented.

The first opening and the second opening may comprise a common shape.The common shape of the first opening and the second opening maycoincide according to the relative orientation of the connected firstring-shaped element and second ring-shaped element.

The through holes and the detachable connection elements may comprise asecond common arrangement. The second common arrangement of the throughholes and the detachable connection elements may coincide according tothe relative orientation of the connected first ring-shaped element andsecond first ring-shaped element.

The detachable connection elements may be adapted to couple to bolts asthe fixing means. The detachable connection elements may comprise or bethreaded holes.

The connecting frame may further comprise an outer sealing element witha shape corresponding to a shape of the second sealing face, adapted tobe arranged between the connected second ring-shaped element and thepropulsion system, and adapted to provide a waterproof connectionbetween the second sealing face and the propulsion system.

The connecting frame may further comprise an inner sealing element witha shape corresponding to a shape of the first sealing face, adapted tobe arranged between the connected first ring-shaped element and secondring-shaped element, and adapted to provide a waterproof connectionbetween the second ring-shaped element and the hull with the opening.

The opening of the connecting frame may have a width of at least 20 cm,in particular of at least 25 cm or of at least 30 cm.

The first width and/or the second width may be at least 20 cm, inparticular at least 25 cm or at least 30 cm.

A connecting system may comprise the connecting frame and a supportelement.

The support element may be adapted to mechanically support thepropulsion system.

The support element may be adapted to define a position and/or an angleof the propulsion system relative to the connecting frame, in particulara distance of a motor and/or a far end of the propulsion system from theconnecting frame.

The support element may be adapted to be connected to the connectingframe, in particular such that the support arm extends away from theconnecting frame.

The support element may be connected to the connecting frame, inparticular such that the support arm extends away from the connectingframe.

The support element may be connected to the connecting in directphysical contact with the connecting frame. The support element may beconnected to the connecting frame permanently or with a detachableconnection.

The support element and a portion of the connecting frame may form anintegral piece.

The support element may comprise a support arm.

The support arm may comprise an elongated shape.

The support arm may extend away from the connecting frame.

The support arm may comprise an upper surface corresponding to a loweredge of the opening of the connecting frame and/or of the first opening.

The upper surface of the support arm may extend away from the lower edgeof the opening of the connecting frame and/or of the first opening.

The support arm may be connected to the connecting frame and/or be indirect physical contact with the connecting frame.

The support element may further comprise a support column extending awayfrom the support arm. The support column may be adapted to mechanicallysupport the propulsion system and/or be in direct physical contact withthe propulsion system. The support column may be connected to thesupport arm and/or be in direct physical contact with the support arm.

In a third aspect, a method is provided for connecting an electricallydriven propulsion system as a whole to a hull with an opening. Theelectrically driven propulsion system comprises an electric motoradapted to provide a mechanical power of at least 50 kW; a transmissionfunctionally coupled to the electric motor, the transmission comprisinga propeller coupling adapted for mounting a propeller; and a commonwaterproof housing. The electric motor and a section of the transmissionare arranged inside the common waterproof housing. The common waterproofhousing comprises a motor section in which the electric motor isarranged. The method comprises providing the electrically drivenpropulsion system as a whole on a second side of the opening of thehull; moving, while keeping the electrically driven propulsion systemassembled as a whole and while keeping the propeller coupling on thesecond side, the motor section through the opening to a first side ofthe opening opposite to the second side; and fixing the electricallydriven propulsion system to the hull with the opening; and forming awaterproof connection between the hull and the common waterproofhousing.

Thus, the electrically driven propulsion system as a whole may beconnected to a hull quickly and reliably. The electrically drivenpropulsion system may be disconnected from the hull just as easily andquickly by performing the reverse of each step and in a reversed orderof the steps. In case of a failure of the electrically driven propulsionsystem, the electrically driven propulsion system as a whole may bechanged by disconnecting the defective electrically driven propulsionsystem and connecting a corresponding, functional electrically drivenpropulsion system. The modular design of the electrically drivenpropulsion system improves the flexibility and speed at which areplacement part may be provided. For example, multiple electricallydriven propulsion systems may be kept in a central storage facility. Incase of a failure of an electrically driven propulsion system installedon a boat, one of the electrically driven propulsion systems may beshipped from the central storage facility to a location of the boat andreplace the electrically driven propulsion systems with the failure. Theoverall duration of the process from receiving the reporting of thefailure at the central storage facility to finishing the replacement ofthe electrically driven propulsion systems 100 on the boat may be short,for example less than 36 hours.

In this process, no mechanical adjustment of the replacementelectrically driven propulsion systems may be requirement. A softwareintegration of the replacement electrically driven propulsion systemsmay be performed through an over-the-air-update.

The method may further comprise, prior to the moving the motor sectionthrough the opening, mounting a connecting frame to the hull with theopening; the fixing the electrically driven propulsion system to thehull with the opening may comprise fixing the electrically drivenpropulsion system to the connecting frame; and the forming thewaterproof connection between the hull and the common waterproof housingmay comprise forming the waterproof connection between the connectingframe and the common waterproof housing.

The common waterproof housing may comprise a ring-shaped seal face, andthe forming the waterproof connection between the hull and the commonwaterproof housing may comprise forming the waterproof connectionbetween the ring-shaped seal face and the hull such that the ring-shapedseal face encircles the opening.

The electrically driven propulsion system may further comprise fixingmeans in direct physical contact with the ring-shaped seal face, and thefixing the electrically driven propulsion system to the hull with theopening may comprise coupling the fixing means to the hull with theopening, in particular to through holes of the hull with the opening.

The forming the waterproof connection between the hull with the openingand the common waterproof housing comprise closing the opening of thehull, in particular in a waterproof way.

The fixing the electrically driven propulsion system to the hull withthe opening may comprise fixing the electrically driven propulsionsystem as a surface drive to the hull with the opening.

A surface drive may provide a high efficiency, i.e., a strong forwardpropulsion per electric power supplied the propulsion system, forexample through the power inlet. This may improve the efficiency of anelectric watercraft comprising the electrically driven propulsionsystem. In particular, a propeller coupling, a propeller shaft or apropeller of a surface drive may have an optimum revolution speedsimilar to a revolution speed of an electric motor such as an axial fluxmotor. Installing the electrically driven propulsion system as a surfacedrive may therefore support the use of a transmission with a small gearratio, which may improve the energy efficiency and thus the rangefurther.

The opening of the hull may be adapted to be at a vertical position of awater line of the hull or of a watercraft comprising the hull.

The water line may refer to a static water line, in particular to awater line of the hull or the watercraft when the hull or the watercraftdoes essentially not move.

The water line may refer to a planing-speed water line, in particular toa water line of the hull or the watercraft when the hull or thewatercraft moves forward at a planing speed and/or at a speed of 30knots. The planing speed may refer to a speed of the hull or thewatercraft, at which the hull or the watercraft is adapted toessentially lift above the static water line.

An upper edge of the opening of the hull may be arranged at a verticalposition corresponding to the static water line of the hull or thewatercraft.

A lower edge of the opening of the hull may be arranged at a verticalposition corresponding to the planing-speed water line of the hull orthe watercraft.

The fixing the electrically driven propulsion system to the hull withthe opening may comprise generating the opening of the hull.

The fixing the electrically driven propulsion system to the hull withthe opening may be performed from the second side. Alternatively, or inaddition, the fixing the electrically driven propulsion system to thehull with the opening may comprise connecting the fixing means to thedetachable connection elements through the through holes of the firstring-shaped element.

The method may comprise fixing the electrically driven propulsion systemto the hull at a vertical position corresponding to a water line of thehull or of the watercraft, in particular, such that an upper end of thepropeller coupling or the propeller is at most 30 cm below the staticwater line, in particular at most 20 cm below the static water line orat most 10 cm below the static water line.

Alternatively, or in addition, the method may comprise fixing theelectrically driven propulsion system to the hull such that a first partof the propeller coupling or the propeller is below a planing-speedwater line of a watercraft comprising the hull, and a remaining part ofthe propeller coupling or the propeller is above the planing-speed waterline of the watercraft.

The electrically driven propulsion system of the method may be formedwith any or all of the features described above in the context of theelectrically driven propulsion system.

The electrically driven propulsion system may further comprise apropeller mounted to the propeller coupling.

BRIEF DESCRIPTION OF THE FIGURES

The techniques of the present disclosure and the advantages associatedtherewith will be apparent from a description of exemplary embodimentsin accordance with the accompanying drawings, in which:

FIG. 1 a shows an electrically driven propulsion system according to anembodiment;

FIG. 1 b shows an application example of the electrically drivenpropulsion system;

FIG. 1 c shows another application example of the electrically drivenpropulsion system;

FIG. 1 d shows another application example of the electrically drivenpropulsion system;

FIG. 2 shows an electrically driven propulsion system according toanother embodiment;

FIG. 3 shows an electrically driven propulsion system according toanother embodiment;

FIG. 4 shows an electrically driven propulsion system according toanother embodiment;

FIG. 5 a shows an electrically driven propulsion system with aconnecting from according to an embodiment;

FIG. 5 b shows an electrically driven propulsion system with aconnecting from according to another embodiment;

FIG. 6 shows an electrically driven propulsion system according toanother embodiment;

FIG. 7 a shows an electrically driven propulsion system according toanother embodiment;

FIG. 7 b shows the electrically driven propulsion system according tothe embodiment of FIG. 7 a;

FIG. 7 c shows the electrically driven propulsion system according tothe embodiment of FIG. 7 a , FIG. 7 b;

FIG. 7 d shows a propeller for surface drive;

FIG. 7 e shows an electrically driven propulsion system according toanother embodiment;

FIG. 8 a shows an electrically driven propulsion system according toanother embodiment;

FIG. 8 b shows the electrically driven propulsion system according tothe embodiment of FIG. 8 a;

FIG. 8 c shows an electric motor according to an embodiment;

FIG. 8 d shows an electric motor according to a different embodiment;

FIG. 9 a shows a method for connecting an electrically driven propulsionsystem to a hull according to an embodiment;

FIG. 9 b shows a method for connecting an electrically driven propulsionsystem to a hull according to another embodiment;

FIG. 9 c shows a method for connecting an electrically driven propulsionsystem to a hull according to another embodiment;

FIG. 10 a shows a side view of a connecting frame;

FIG. 10 b shows a front view of the connecting frame; and

FIG. 11 shows a hull prepared for connecting the electrically drivenpropulsion system as a surface drive.

DETAILED DESCRIPTION

FIG. 1 a shows an electrically driven propulsion system 100 according toan embodiment. The propulsion system 100 forms a monolithic unitcomprising the electric motor 102 and a transmission 106 coupled to theelectric motor 102, as well as a pulse inverter 118 providing anelectrical supply power to the electric motor 102. A correspondingelectrically driven propulsion system 100 is also referred to as anintegrated propulsion system 100.

The transmission 106 comprises an encased section 106 e inside thehousing 108, as well as an external section 106 x outside of thewaterproof housing 108 at its far end from the motor 102. Thetransmission 106 rotationally couples the external section 106 x to theelectric motor 102 via the encase section 106 e, hence transferring arotational movement of the electric motor 102 out of the housing 108. Itcomprises any component required for this purpose. According to theexample depicted in FIG. 1 a , this is a (rotary) shaft 106.

The electrically driven propulsion system 100 further comprises a thrustbearing 164. When the electric motor 102 is driven with electric outputpower from the pulse inverter 118 to rotate a rotary shaft 106 of thetransmission, this movement causes a propeller of the watercraft torotate. The propeller is coupled to the rotary shaft 106 directly or viaa drive provided by the watercraft.

The rotation of the propeller results in a forward force 166, or apropulsion 166, respectively, of the rotary shaft 106 along its axialdirection 168. The thrust bearing 164 transfers this force 166 onto thehousing, thereby generating a propulsion 166′ of the housing andultimately of the watercraft. Therefore, the thrust bearing 164 isconnected to the rotary shaft 106 and to the housing to couple the tworotationally, i. e. its inner ring is rigidly connected to the rotaryshaft 106 and its outer ring of the bearing is rigidly connected to thehousing 108.

The monolithic design of the electrically driven propulsion system 100allows for equipping a watercraft with the electrically drivenpropulsion system 100 in a few simple steps. The components of thesystem 100, i. e. the electric motor 102, the inverter 118, thetransmission 106, and the thrust bearing 164 are fully optimized withrespect to each other. Therefore, by equipping his or her watercraftwith the electrically driven propulsion system 100, a user installs ahigh-power, high-efficiency system for an optimized range of thewatercraft. No further selection of additional components and nocorresponding expert knowledge is required, and the risk of losingefficiency or range is eliminated.

Moreover, the integrated (monolithic) design allows for replacing it asa whole quickly and easily in case of a failure of one of thecomponents, i. e. with all essential components mounted in theirrespective locations for operation. The defective component may bediagnosed and replaced later, for example in a dedicated facility, asthe watercraft with the replaced propulsion system is already back inoperation. The monolithic unit 100 may be mechanically sealed or lockedto prevent a user from opening it and to permit access only in acontrolled environment, such as a maintenance and repair facility.

Any need to disassemble or assemble any component of the electricallydriven propulsion system 100 at the location of the watercraft isavoided. The installation or replacement may reliably be performed by aperson without specialized skills and knowledge of any of the componentsof the electrically driven propulsion system 100.

In a preferred embodiment, the electric motor 102 is an axial fluxmotor. Axial flux motors are particularly light-weight and compact, forexample compared to radial flux motors. Therefore, the use of an axialflux motor renders the installation and exchange of the integratedpropulsion system 100 as a hole way more manageable and secure. Theaxial flux motors 102 operate at relatively low revolution speeds of1500 to 3500 rounds per minute, similar to the optimal revolution speedof the propeller, for example for a surface drive. Consequently, theintegrated propulsion system 100 may in principle be formed without anygearing mechanism or ratio between the electric motor 102 and itsexternal section 106 x.

Depending on the embodiment, it provides a mechanical power of 100 kW or200 kW. The axial flux motor 102 adapted to provide the mechanical powerof 100 kW has a weight of 25 kg, and the axial flux motor 102 adapted toprovide the mechanical power of 200 kW has a weight of 50 kg.

The common waterproof housing 108 protects the components it surroundsfrom external influences, such as seawater or weather conditions, inparticular on the watercraft. On the other hand, the housing 108protects a user from electrical hazards related to the electric motor102, in particular on the inside 216 of the hull 202. For this purpose,the housing 108 comprises a layer of insulating material or a layer ofgrounded, conductive material.

Moreover, the common waterproof housing 108 provides an acousticshielding for the motor and the enclosed section 106 e of thetransmission, and reduces noise on board emerging from those components.

The integrated propulsion system 100 is compatible with various boatlayouts, and optimized embodiments for a number of layouts will bepresented throughout this description. FIG. 1 b , FIG. 1 c , and FIG. 1d illustrate application examples.

According to FIG. 1 b , the integrated propulsion system 100 isinstalled in a watercraft with a fixed shaft. The transmission 106 ofthe integrated propulsion system 100 connects directly to the fixedshaft, and is optimized for this purpose with a planetary gearing 106 bproviding a gear ratio optimized for the watercraft. The system comes asa kit with a support structure 128 to adjust the integrated propulsionsystem 100 to the inclination angle of the fixed shaft.

According to FIG. 1 c , the integrated propulsion system 100 isinstalled as a component of a sail drive for a sailing boat. The shaft106 of the propulsion system 100 connects to an input gear of a spurgear of the sail drive. There, the electrically driven propulsion system100 may replace a combustion engine to reduce the noise level on boardand improve the sustainability of the sailing boat.

According to FIG. 1 d , the integrated propulsion system 100 isinstalled at the transom 202 of the watercraft, preferably as a surfacedrive. The propulsion system 100 pierces through the transom 202 and isarranged part inside, part outside of the watercraft.

The external section 106 e of the transmission comprises a propellercoupling 106 c for mounting a propeller. The system 100 thereforeincludes any mechanical component required to couple the propeller shaft106 e, or the propeller coupling 106 c, respectively (and ultimately apropeller mounted to the coupling 106 c) rotationally to the electricmotor 102. In the following, such a system 100 is referred to a fullymechanically integrated.

This option is particularly favorable for high-speed watercraft, forexample with a cruising speed of 20 to 50 kn. The system comes as a kitwith a support structure 128 to adjust the integrated propulsion system100 to the optimum inclination angle of the surface drive.

FIG. 2 shows an integrated propulsion system 100 according to anotherembodiment. The integrated propulsion system 100 of FIG. 2 is similar tothe one of FIG. 1 a . Similar elements are indicated by same referencenumerals and will not be described again. The integrated propulsionsystem 100 of FIG. 2 is designed with a series of modifications.According to different embodiments, the electrically driven propulsionsystem 100 is formed with any single one or any combination of thedescribed modifications.

The integrated propulsion system comprises two noise/vibration sensors152, which detect a sound level or a sound pattern of the system 100,generate a corresponding electronic signal, and send it through a signalline 154 out of the system and to a signal processor 156 of the system.

The signal processor 156 or an external processor connected to thesignal line 154 detects changes in the sound level or sound pattern ofthe system 100.

When a permanent change is detected, it may be an indication for anupcoming failure, for example you to an increased friction betweenelements of the system 100. The processor 156 generates an electronicreport message, indicating that the integrated propulsion system 100 mayneed to be replaced.

When a sudden change in the sound level or the sound pattern of thesystem 100 is detected and exceeds a critical level, this may be anindication of a contact or a collision of the watercraft with anobstacle. The processor 156 generates an electronic warning message,which may for example trigger an alarm or a transmission of an emergencymessage, for example via a long-distance network.

The signal line 154 is shown only for one of the sensors 152, but isequally formed for the second one.

Two signal lines 154 are shown, one leading to the processor 156 and oneleading out of the housing 108, but according to different embodiments,only one of the two is formed.

One of the noise/vibration sensors 152 is arranged in direct contactwith the electric motor 102, to specifically monitor changes in thesound level or sound pattern of the electric motor. The othernoise/vibration sensor 152 is arranged at a far end of the housing 108from the motor 102 in direct contact with the housing. In embodiments,wherein the far end of the housing 108 is in contact with a surroundingbody of water, such as the embodiment of FIG. 1 d , this noise/vibrationsensor 152 monitors body sound transferred by the water. Additionalnoise/vibration sensors 152 may be provided, for example in the vicinityor in direct contact with individual components of the transmission 106,or only one of the noise/vibration sensors 152 may be present.

FIG. 3 shows an integrated propulsion system 100 according to anotherembodiment. The integrated propulsion system 100 of FIG. 3 is similar tothe one of FIG. 1 a and FIG. 2 . Similar elements are indicated by samereference numerals and will not be described again. The integratedpropulsion system 100 of FIG. 3 is designed with a series ofmodifications. According to different embodiments, the electricallydriven propulsion system 100 is formed with any single one or anycombination of the described modifications.

The transmission 106 of the electrically driven propulsion system 100 ofFIG. 3 comprises a planetary gearing 106 b to implement a gear ratiobetween a second (rotary) shaft 106 c and a first (rotary) shaft 106 aof the transmission. The first shaft 106 a is coupled to the electricmotor 102 and forms a motor shaft 106 a. The second shaft 106 c maycarry a propeller 104 or propeller coupling 106 c like in the example ofFIG. 1 d or be connected to an external transmission like in theembodiments of FIG. 1 b , FIG. 1 c.

The transmission serves to match the highest-efficiency rotation speedof the second shaft 106 c to the highest-efficiency rotation speed ofthe propeller 104 or the external transmission. The highest efficiencyrotation speed of the second shaft 106 c refers to the rotation speed ofthe second shaft 106 c, at which the overall electrical power tomechanical power conversion efficiency of the integrated propulsionsystem 100 is maximum. Mechanical power refers to the mechanical powergenerated at the second shaft 106 c due to its rotational movement. Theelectrical power refers to an input power provided to the pulse inverter118 via a power inlet of the pulse inverter from an external currentsource, such as a battery.

The electrically driven propulsion system 100 of FIG. 3 furthercomprises a heat exchanger 122.

The heat exchanger 122 is thermally coupled via its secondary side 126to any component of the system 100 requiring cooling, in particular theelectric motor 102, but also to the pulse inverter 118, the transmission106 or a thrust bearing (not shown) as required. The secondary side 126of the heat exchanger comprises cooling channels 126 c filled with acoolant and connecting the heat exchanger 122 to the respectivecomponents. The coolant has an optimized composition comprises asufficient amount of glycol to prevent freezing in any relevantsituation. The heat exchanger further comprises a coolant pump (notshown) to generate a flow of the coolant in the channels 126 c of itssecondary side 126.

The secondary side 126 of the heat exchanger 122 further provides twoopenings 1260, namely an outlet and an inlet for coolant to an externaldevice, such as a battery or a cabin. If not required, the openings 1260are bridged.

A primary side 124 of the heat exchanger 122 connects to openings 1240outside the housing 108. In operation, the openings 1240 are eitherdirectly exposed to a body of water surrounding the watercraft and takeup water as a coolant therefrom. Alternatively, the openings 1240 areconnected to the surrounding body of water using additional externaltubing, for example through a feedthrough in the hull of the watercraft.A coolant pump (not shown) ensures a sufficient flow of water at theprimary side 124 of the heat exchanger 122.

FIG. 4 shows an integrated propulsion system 100 according to anotherembodiment. The integrated propulsion system 100 of FIG. 4 is similar tothe one of FIG. 1 a , FIG. 2 , and FIG. 3 . Similar elements areindicated by same reference numerals and will not be described again.The integrated propulsion system 100 of FIG. 4 is designed with a seriesof modifications. According to different embodiments, the electricallydriven propulsion system 100 is formed with any single one or anycombination of the described modifications.

According to the embodiment of FIG. 4 , the housing 108 of theelectrically driven propulsion system 100 comprises a fore (motor)section 108 a wherein the motor is arranged and an aft (transmission)section 108 b wherein the encased section 106 e of the transmission 106is arranged.

The transmission section 108 b has a larger width w1 than the motorsection w2. The widths w1, w2 refer to widths of the respective crosssections of the housing 108, for example in the planes 160, 162perpendicular to the longitudinal direction 158 of the system 100intersecting the housing 108 at different positions along thelongitudinal direction 158.

The embodiment of FIG. 4 is preferably mounted to a transom 202 of awatercraft. The fore (motor) section 108 a is located directly fore ofthe aft (transmission) section 108 b and its cross section is completelycomprised in a fore projection of the aft (transmission) section 108 b.

Therefore, when the integrated propulsion system 100 is inserted intothe transom 202 through an opening 204, the motor section 108 a is takenup completely by the watercraft, whereas the transmission section 108 bserves as a stopper to define the depth to which the integratedpropulsion system 100 is introduced. A portion of the transmissionsection 108 b remains outside of the watercraft.

A seal (not shown) between the housing 108 and the hull 202 ensures awaterproof connection.

Thus, an ideal geometry is realized for a surface drive, with thepropeller coupling 106 c aft of the transom 202 and the entire hull. Thesurface drive is particularly energy efficient for high speeds exceeding20 kn, making the integrated propulsion system 100 attractive forhigh-speed, electrically driven watercraft. The high efficiency of thesurface drive helps to make best possible use of the charge capacity ofthe battery and to improve the range of the high-speed, electricallydriven watercraft.

To further optimize the integrated propulsion system 100 of FIG. 4 forthis purpose, it is designed with a linear arrangement along itslongitudinal direction 158, which pierces through the opening 204 of thehull 202. In other words, the electric motor 102, the shaft 106 and thepropeller coupling 106 p are all intersected by a single line extendingalong the longitudinal direction 158. In this embodiment, thelongitudinal direction of the integrated propulsion system coincideswith the axis of the shaft 106 coupled to the motor 102, and with ahorizontal axis x perpendicular to a vertical axis z and a secondhorizontal axis y.

FIG. 5 a shows an integrated propulsion system 100 according to anotherembodiment. The integrated propulsion system 100 of FIG. 5 a is similarto the one of FIG. 1 a , FIG. 2 , FIG. 3 , and FIG. 4 .

Similar elements are indicated by same reference numerals and will notbe described again. The integrated propulsion system 100 of FIG. 5 a isdesigned with a series of modifications. According to differentembodiments, the electrically driven propulsion system 100 is formedwith any single one or any combination of the described modifications.

While the integrated propulsion system 100 of the embodiment of FIG. 4is shown as mounted directly to the hull 202, a connecting frame 302 isprovided between the integrated propulsion system 100 of FIG. 5 a andthe hull 202. The integrated propulsion system 100 is mounted to theconnecting frame 302.

The connecting frame 302 comprises a first ring-shaped element 308 onthe inside 216 of the hull 202 and second ring-shaped element 308 on theoutside 210 of the hull 202.

Threaded holes 318 of the second ring-shaped element 308 and slightlylarger through holes 316 of the first ring-shaped element 306 facilitatea connection between the two. Through holes similar to the ones 316 ofthe first ring-shaped element 306 are formed in the hull 202. Connectingthe ring-shaped elements 306, 308 with bolts 322 clamps them to the hull202, and sealing rings (not shown) between the ring-shaped elements 306,308 and the hull 202 establish a waterproof connection between theconnecting frame 302, 306, 308 and the hull 202.

The integrated propulsion system 100 of FIG. 5 a comprises through holes110 a formed on a ring-shaped sealing face 110 .

The ring-shaped elements 306, 308 further comprise through holes 320 aand threaded holes 320 b, which serve to establish a detachableconnection. The arrangements of both the through holes 320 a and thethreaded holes 320 b correspond to the arrangement of the through holes110 a of the ring-shaped sealing face 110. Therefore, inserting bolts222 through the through holes 110 a and the trough holes 320 a andtightening them to the threaded holes 320 b connects the integratedpropulsion system 100 to the hull 202. A sealing ring (not shown)between the sealing face 110 and the second ring-shaped elements 306ensures a waterproof connection between the two.

A corresponding connection using a connecting frame 302 is optionallyand preferably also applied in any of the other embodiments. It ensuresa reliably detachable connection between the electrically drivenpropulsion system 100 and the watercraft, without any risk of touchingor damaging the watercraft, in particular its hull 204, in the processof attach or detaching the electrically driven propulsion system 100from or to the watercraft.

The connecting frame 302 permits to install and remove the integratedpropulsion system 100 from outside of the watercraft using a detachableconnection, thus avoiding any need to work inside the typically narrowinside space of the watercraft, or its hull, respectively.

According to the embodiment of FIG. 5 a , the thrust bearing 164provides a waterproof connection between the housing 108 and the rotaryshaft 106, and therefore forms a section of the common waterproofhousing. In other words, a section of the thrust bearing 164 is arrangedin a wall of the waterproof housing 108.

FIG. 5 b shows an integrated propulsion system 100 according to anotherembodiment. The integrated propulsion system 100 of FIG. 5 b is similarto the one of FIG. 1 a , FIG. 2 , FIG. 3 , FIG. 4 , and FIG. 5 a .Similar elements are indicated by same reference numerals and will notbe described again. The integrated propulsion system 100 of FIG. 5 b isdesigned with a series of modifications.

According to different embodiments, the electrically driven propulsionsystem 100 is formed with any single one or any combination of thedescribed modifications.

According to the embodiment of FIG. 5 b , a connecting system isestablished by combining the connecting frame 302 with a support element128 connected to the frame 128.

The support element 128 comprises a support arm 128 a which is connectedto and extends away from the connecting frame 302. It further comprisesa support column 128 b, which is connected to and extends away from thesupport arm 128 in the vertical direction z. The support column isadapted to support the integrated propulsion system 100 at its housing108.

The support element 128 reduces vibrations of the housing 108, of theintegrated propulsion system 100, and in particular of the electricmotor 102. This reduces undesired noise emerging from the unit andimproves its reliability and lifetime. Moreover, the length of thesupport arm 128 a is preselected according to the length of the portionof the integrated propulsion system 100 to be inserted into the hull202, such that the support arm 128 a helps to define a mounting depth ofthe integrated propulsion system 100 in the hull 202. The supportelement 128 therefore renders the mounting of the electrically drivenpropulsion system 100 more simple and reliable.

The support arm 128 a extend away from the connecting frame 302, morespecifically from the lower edge of the opening 304 of the connectingframe 302. Therefore, when the propulsion system 100 is inserted intothe watercraft through the transom 202 with the opening 204 along thedirection x, the support arm 128 a serves to guide the movement of thepropulsion system 100 and restrains it along both the vertical directionz and a horizontal sidewards direction y. Therefore, the system 100 maybe inserted into the watercraft with a minimum of force, in particularwith much less force than would be required to stabilize the position ofthe system 100 without the guiding arm 128 (e. g. along the verticaldirection z). Moreover, the support arm 128 a may guide the movement ofthe system 100 along a straight trajectory x and avoid unwantedmovements along the sidewards direction y.

The integrated propulsion system 100 according to the embodiment of FIG.5 b further comprises anti-mechanical-shock elements (not shown) tomechanically insulate the electric motor 102 from the housing 108. Theanti-mechanical-shock elements are arranged inside the housing 108 andbetween the housing 108 and the motor 102. The comprise support elementsmade from a material with a high internal friction, for examplecomprising viton. They further improve the noise level, reliability, andlifetime of the electric motor 102. Corresponding anti-mechanical-shockelements are optionally and preferably applied in any of the otherembodiments.

FIG. 6 shows an integrated propulsion system 100 according to anotherembodiment. The integrated propulsion system 100 of FIG. 6 is similar tothe one of FIG. 1 a , FIG. 2 , FIG. 3 , FIG. 4 , FIG. 5 a and FIG. 5 b .Similar elements are indicated by same reference numerals and will notbe described again. The integrated propulsion system 100 of FIG. 6 isdesigned with a series of modifications. According to differentembodiments, the electrically driven propulsion system 100 is formedwith any single one or any combination of the described modifications.

The electrically driven propulsion system 100 of FIG. 6 comprises agearing mechanism 106 b similar to the one described in the context ofthe embodiment of FIG. 3 . However, as opposed to the gearing mechanism106 b of FIG. 3 , which provides a coupling between the first shaft andthe second shaft along a continuous line, the gearing mechanism 106 b ofFIG. 6 provides an offset 130, or a displacement 130, respectively,between the first shaft and the second shaft along a directionperpendicular to their respective axes.

The offset 130 in the embodiment of FIG. 6 is implemented by using aspur gear in the gearing mechanism 106 b, alone or in combination withthe planetary gear described above.

The offset 130 improves the design flexibility of the system 100. Inparticular, it helps to lower the propeller coupling 106 c to the waterline of the watercraft.

The electrically driven propulsion system 100 of FIG. 6 furthercomprises a noise/vibration sensor 152 arranged outside 210 of thewatercraft and below the propeller shaft 106 c and the propellercoupling 106 p, and therefore below the water line of the watercraft. Asdescribed above, this arrangement of the noise/vibration sensor 152allows for capturing body sound from a body of water surrounding thewatercraft.

FIG. 7 a , FIG. 7 b , and FIG. 7 c show an integrated propulsion system100 according to another embodiment. The integrated propulsion system100 of FIG. 7 a , FIG. 7 b , and FIG. 7 c is similar to the one of FIG.1 a , FIG. 2 , FIG. 3 , FIG. 4 , FIG. 5 a , FIG. 5 b and FIG. 6 .Similar elements are indicated by same reference numerals and will notbe described again. The integrated propulsion system 100 of FIG. 7 a ,FIG. 7 b , and FIG. 7 c is designed with a series of modifications.According to different embodiments, the electrically driven propulsionsystem 100 is formed with any single one or any combination of thedescribed modifications.

The embodiment of FIG. 7 a , FIG. 7 b , and FIG. 7 c uses two axial fluxmotors 102. An electric supply power is provided to the axial fluxmotors 102 by the pulse inverter 118. The pulse inverter 118 receivesits input power from a power inlet 120 fed through the waterproofhousing 108 in a waterproof manner to connect a battery outside of thehousing 108. When the electrically driven propulsion system 100 ismounted to the watercraft, the power inlet 120 is located inside thewatercraft and accessible there.

A watercraft battery providing a DC voltage may be connected to thepower inlet 120. The pulse inverter 118 generates the AC electricalsupply current for the electric motors 102 from the DC voltage. Thepulse inverter 118 is also coupled to a data line 116 to receive controlcommands and software updates, such as updates of parameters related tothe operation of the pulse inverter 118.

Axial flux motors may be constructed with higher power densities thanconventional engines and electric motors, such as radial flux motors. Asthe revolution speed of the axial flux motors 102 is similar to theoptimal revolution speed of the propeller 104, the gearbox 106 b mayhave a small gear ratio, such as a gear ratio of 1.18, and thus a higherefficiency than a gearbox with a high gear ratio typically applied incombination with an engine or an electric motor with a higher revolutionspeed.

The common waterproof housing 108 provides a motor section 108 a for theelectric motor on a first side 216 of a sealing face 110, and atransmission section 108 b on the opposite, second side 210 of thesealing face 110. Threaded holes 110 a are formed on the sealing face110. The transmission section 108 b contains a section of the propellershaft 106 c and a section of the gearbox 106 b. Other parts of thetransmission 106, namely the motor shaft 106 a and most of the gearbox106 b, are placed inside the motor section 108 b.

Consequently, when the electrically driven propulsion system 100 isconnected with its sealing face 110 to a hull 202, the electric motors102 are located inside of the hull 202 where they are protected fromenvironmental influences and acoustically shielded to minimize a noiselevel on board and on deck.

The electrically driven propulsion system 100 also comprises anelectromechanical rudder actuator 112 arranged in the common waterproofhousing 108. The electromechanical rudder actuator 112 actuates rudders114 b, 114 s arranged portside and starboard of the propeller 104.Therefore, the electromechanical rudder actuator 112 receives anelectrical signal from a data line 116. The data line 116 ends in a datainput connector 116 c.

The data input connector 116 c is arranged on the common waterproofhousing 108 to provide access from outside of the common waterproofhousing 108. The data input connector 116 c is sealed against the commonwaterproof housing 108 in a waterproof way. The data line 116 is alsoused for software update, such as updates of parameters related to theoperation of the electromechanical rudder actuator 112.

The electrically driven propulsion system according to the embodiment ofFIG. 7 a , FIG. 7 b , and FIG. 7 c further comprises a propeller 104optimized for a surface drive.

FIG. 7 c and FIG. 7 d illustrate the design of the propeller 104designed for the surface drive.

Referring to FIG. 7 c , which shows a stern projection of the integratedpropulsion system 100, the propeller 100 comprises a radial sections 144extending away from the center of the propeller 104, which is mounted tothe propeller coupling 106 p.

An essentially flat section 146 extends away from the radial section 144along the azimuthal direction of the propeller 104 with an angle β ofessentially 90° between the radial section 144 and an outer edge of theessentially flat section 146 e.

Referring to FIG. 7 d , which shows a side view of the integratedpropulsion system 100, the essentially flat section 146, or its outeredge 146 e, respectively, are formed at an angle γ with respect to thelongitudinal direction of the propeller 104. The angle γ is defined bythe pitch 150 and the diameter 148 of the propeller 104. In particular,the tangent of the angle γ is the diameter 148 over half the pitch 150.

FIG. 7 e shows an integrated propulsion system 100 according to anotherembodiment. The integrated propulsion system 100 of FIG. 7 e is similarto the one of FIG. 7 a , FIG. 7 b , and FIG. 7 c . Similar elements areindicated by same reference numerals and will not be described again.

As compared to the embodiment of FIG. 7 a , FIG. 7 b , and FIG. 7 c ,the embodiment of FIG. 7 e comprises a single electric motor of 102instead of two electric motors. Instead of the second electric motor,the embodiment of FIG. 7 e comprises a motor upgrade space 138 toreceive an additional electric motor if required.

Such an embodiment improves the design flexibility of the integratedpropulsion system 100, making use of the applied axial flux motor 102.The geometry of the axial flux motor 102 beneficially permits to add orremove an electric motor and thus improves the design flexibility andthe modularity of the electrically driven propulsion system 100.

All other components, in particular the pulse inverter 118 and thetransmission 106, are provided for with specification in terms ofelectrical and mechanical power corresponding to the integratedpropulsion system 100 with the maximum number of electric motors 102.

According to the embodiment depicted in FIG. 7 e , the motor section 108a has space for two electric motors. It comprises one electric motor 102and an upgrade space 138 for one additional electric motor. However,according to alternative embodiments, the motor section 108 a providesspace for two, four or more electric motors 102. The motor section 108 amay comprise a single electric motor 102, and additional electric motorsmay be added in a modular way as needed to increase the overall maximumpower of the electrically driven propulsion system 100. For maximumflexibility, any of the electric motors is preferably exchangeable withany other of the electric motors 102, i. e. the electric motors and theadditional electric motors have similar physical dimensions andelectrical characteristics.

FIG. 8 a and FIG. 8 b show an integrated propulsion system 100 accordingto another embodiment. The integrated propulsion system 100 of FIG. 8 aand FIG. 8 b is similar to the one of FIG. 7 a , FIG. 7 b , and FIG. 7 c. Similar elements are indicated by same reference numerals and will notbe described again. The integrated propulsion system 100 of FIG. 8 a andFIG. 8 b is designed with a series of modifications. According todifferent embodiments, the electrically driven propulsion system 100 isformed with any single one or any combination of the describedmodifications.

The embodiment of FIG. 8 a and FIG. 8 b further comprises anelectromechanical rudder actuator 112, which receives signals from thedata input connector 116 c. The rudder actuator 112 actuates a centraltiller arm 134 in response to the received signals. The movement of thecentral tiller arm 134 actuates a starboard tiller arm 134 s and aportside tiller arm (not shown), thereby actuating a starboard rudder114 s and a portside rudder (not shown).

According to a corresponding embodiment, the electrically drivenpropulsion system 100 does not only integrate the propulsion as such,but also the steering of the watercraft. The entire unit is provided asa monolithic and fully optimized system. Thus, it renders installing theelectrically driven propulsion system 100 as easy as possible, forexample as a surface drive.

As compared to the embodiment of FIG. 7 a , FIG. 7 b , and FIG. 7 c ,the embodiment of FIG. 8 a and FIG. 8 b comprises a single electricmotor 102, i. e. an electric motor 102 with a single housing.Nevertheless, a motor upgrade is possible, namely making use of anupgrade space in the housing of the electric motor 102.

FIG. 8 c and FIG. 8 d are detailed views of embodiments of electricmotors 102 corresponding to the one of FIG. 8 a and FIG. 8 b.

The electric motor 102 of FIG. 8 c comprises a stator 140 with windingsof electric lines to drive the currents with windings and generate anelectric field at the stator 140. The electric motor 102 furthercomprises rotors 142 with permanent magnets, arranged rotatably on anaxis (not shown).

The electric motor 102 of FIG. 8 d is similar to the electric motor ofFIG. 8 c . However, the electric motor of FIG. 8 d comprises only onerotor 142 and a motor upgrade space 138 instead of the second motor. Therotor upgrade space 142 and hence the electric motor 102 may be upgradedwith the second rotor 142.

According to the embodiments of FIG. 8 c and FIG. 8 d , the electricmotor 102 provides space for two rotors 102, and two or one rotor(s) is(are) provided. However, according to alternative embodiments, theelectric motor 102 is designed for three, four, five, six seven eight,or more rotors 142. It may initially comprise one, two, three, four, ormore rotors 142.

According to a different embodiment (not shown), the electrically drivenpropulsion system comprises a motor space 108 a for a plurality ofmotors 102, such as in FIG. 7 a , FIG. 7 e . Each single motor may havea modular design with a plurality of motors, as described in the contextof FIG. 8 c , FIG. 8 d.

FIG. 9 a and FIG. 9 b illustrate a method 200 for connecting theelectrically driven propulsion system 100 to a hull 202 with an opening204, more specifically to the transom 202 of the hull. The electricallydriven propulsion system 100 may be connected directly to the transom202 with the opening 204. Optionally, a connecting frame 302 with anopening 304 matched to the opening 204 in the transom 202 may be mountedto the transom 202 prior to connecting the electrically drivenpropulsion system 100.

The connecting frame 302 allows for a quick, reliable and safe exchangeof the electrically driven propulsion system 100 as a whole. Inparticular, the risk of damaging the hull 202 is reduced, as anyphysical contact between moving components and the hull 202 isprevented.

The connecting frame 302 according to the embodiment of FIG. 9 a andFIG. 9 b comprises a first ring-shaped element 306 mounted to theoutside 210 of the watercraft, a second ring-shaped element 308 mountedto the inside 216 of the watercraft, and a seal 312 between a sealingface 310 of the first ring-shaped element 306 on the one side and thesecond ring-shaped element 308 as well as the transom 202 on the other.

In a first step, the electrically driven propulsion system 100 is placedon the outside 210 of the watercraft. A seal 212 is provided between thesealing face 110 and the hull 202.

In a second step 214, the motor section 108 a of the electrically drivenpropulsion system 100 with the electric motors 102 is moved 214 throughthe opening 204 in the transom 202, and, if installed, through theopening 304 of the connecting frame 302, to the inside 216 of thewatercraft. The propeller coupling 106 p and the propeller 104 remain onthe outside 210 of the watercraft.

In a third step 218 a, 218 b, the electrically driven propulsion system100 is fixed 218 to the transom 202 and, if installed, to the connectingframe 302. To this end, through holes 110 a, 220, 320 a may be providedin the (sealing face 100 of the) propulsion system 100, transom 202 andthe connecting frame 302. Via these through holes, bolts 222 areinserted 218 a and screwed 218 b into the threaded holes 320 b in the(second ring-shaped element 308 of the) connecting frame 302 toimplement the fixing 218. In embodiments without a connecting frame 302(not shown), nuts on the inside 216 of the watercraft provide thethreaded holes 320 b.

In a fourth step, a waterproof connection is formed between the commonwaterproof housing 108 of the electrically driven propulsion system 100and the transom 202 or, if installed, the connecting frame 302.Therefore, the bolts 222 are screwed 218 b into the threaded holes 320 awith a defined torque and with the seal 212 between the sealing face 110and the transom 202 or the connecting frame 302, respectively.

Thus, the electrically driven propulsion system 100 may be connected toa watercraft in a few quick and simple steps. The electrically drivenpropulsion system 100 may be disconnected from the watercraft just aseasily and quickly by performing the reverse of each step and in areversed order of the steps. In case of a failure of the electricallydriven propulsion system 100, for example related to the failure of oneof the electric motors 102 or of the transmission 106, the electricallydriven propulsion system 100 may be changed as a whole by disconnectingthe defective electrically driven propulsion system 100 and connecting acorresponding replacement part. The modular design of the electricallydriven propulsion system 100 allows for providing the replacement partmore quickly and efficiently.

For example, multiple electrically driven propulsion systems 100 may bekept in a central storage facility. In case of a failure of anelectrically driven propulsion system 100 installed on a boat somewherein the world, one of the multiple electrically driven propulsion systems100 may be just slightly modified in the central storage facility forthe use as a replacement part for the defective system, for example byinstalling a suitable number of electric motors 102.

Subsequently, the replacement part may be shipped to a location of theboat and replace the electrically driven propulsion system 100 with thefailure. The overall duration of the process from learning of thefailure at the central storage facility to finishing the replacement ofthe electrically driven propulsion systems 100 on the boat may be short,for example less than 36 hours.

FIG. 9 c summarizes the most important steps of the method 200.

In step 230, the electrically driven propulsion system 100 is providedas a whole on a second side 210 of the opening 204 of the hull 202.

In step 214, at least a section of the motor section 108 a is moved,while keeping the electrically driven propulsion system 100 assembled asa whole and while keeping the propeller coupling 106 p on the secondside 210, through the opening 204 to a first side 216 of the opening 204opposite to the second side 210.

In step 218, the electrically driven propulsion system 100 is fixed 218a, 218 b to the hull 202 with the opening 204.

In step 232, a waterproof connection is formed between the hull 202 andthe common waterproof housing 108.

FIG. 10 a and FIG. 10 b depict a connecting frame 302 according to anembodiment. Similar to the embodiment depicted in FIG. 9 a and FIG. 9 b, the connecting frame 302 comprises the first ring-shaped element 306and the second ring-shaped element 308 with essentially identical shapesin a plane perpendicular to the longitudinal direction. The firstring-shaped element 306 and the second ring-shaped element 308 eachcomprise an opening 304 a, 304 b with an essentially identical shape.Threaded holes 316 in the first ring-shaped element 306 and throughholes 318 in the second ring-shaped element 308 with identicalarrangements serve as connecting means to connect the first ring-shapedelement 306 and the second ring-shaped element 308 to each other usingbolts 322. The first ring-shaped element 306 further comprises throughholes 320 a with a predefined arrangement, and the second ring-shapedelement 308 comprises threaded holes 320 b with the same arrangement.

When the first ring-shaped element 306 and the second ring-shapedelement 308 are connected to each other using the through holes 318, thethreaded holes 316, and the bolts 322, the openings 304 a, 304 b overlapto form an opening 304 of the connecting frame 302. For mounting theconnecting frame 302 to the transom 202, the opening 204 of the transom202 is formed to match the shape of the openings 304, 304 a, 304 b.

A first sealing face 310 is formed on the first ring-shaped element 306to form a waterproof connection between the connecting frame 302 and thehull. Therefore, the first ring-shaped element 306 and the secondring-shaped element 308 are connected to each other with the hull 202between them and the seal 312 between the hull 202 and the first sealingface 310.

When the first ring-shaped element 306 and the second ring-shapedelement 308 are connected using the connecting means 316, 318, thethrough holes 320 a and the threaded holes 320 b overlap due to theiridentical arrangements. This allows for connecting the electricallydriven propulsion system 100 to the connecting frame 302 by pushing 218a the bolts 222 through the (through holes 110 a of the sealing face 110of the electrically driven propulsion system 100 and the) through holes320 a and screwing 218 b them into the threaded holes 320 b. The firstring-shaped element 306 further comprises a second sealing face 320 on aface pointing away from the first sealing face 310. When theelectrically driven propulsion system 100 is connected to the connectingframe 302 with the seal 212 between the sealing face 110 of theelectrically driven propulsion system 100 and the second sealing face320 of the first ring-shaped element, a waterproof connection may beformed by screwing the bolts 222 into the threaded holes 320 b with adefined torque.

FIG. 11 illustrates a transom 202 of a hull 404 prepared for connectingthe electrically driven propulsion system 100 as a surface drive.Therefore, an opening 204 is generated in the hull 404, typically in thetransom 202 in the lower region of the transom 202.

An upper edge 402 of the opening is formed in a proximity of a staticwater line 400 of the hull 404, or of a watercraft comprising the hull404, respectively. The static water line 400 refers to the water linewhen the hull or watercraft is not moving.

Watercraft with a surface drive typically has a high cruising speed anda hull adapted for planing. When the watercraft moves at/above itsplanning speed, the transom 202 lifts up, resulting in a lower waterline 400′. The opening 204 is formed with its lower edge at the level ofthis lower, planing-speed water line 400′.

Through holes 220 are formed around the opening 204 in an arrangementmatching the arrangement of the through holes 110 a on the sealing face100 of the electrically driven propulsion system 100, or of the throughholes 320 a or the threaded holes 320 b of the connecting frame 302,respectively. The electrically driven propulsion system 100 may beconnected to the hull 202 by pushing 218 a bolts 222 through the throughholes 110 a and 220 (and the through holes 320 a of a connecting frame302, if installed) and screwing 218 a them into the threaded holes 320 bas described in the context of FIG. 9 a , FIG. 9 b , and FIG. 9 c.

When the electrically driven propulsion system 100 is connected to thehull 404 according to this embodiment, the propeller coupling 106 c, orthe propeller 104, respectively, is arranged in the proximity of theplaning-speed water line 400′. When a propeller 104 is installed, partof the propeller 104 is below the planing-speed water line 400′, whereasthe remaining part of the propeller 104 is above the planing-speed waterline 400′, as is characteristic of a surface drive. However, withrespect to the resting watercraft, propeller coupling 106 c andpropeller 104 are in a vicinity of the static water line 400 below thestatic water line 400, typically up to 10 or 20 cm below the staticwater line 400.

A surface drive may provide a high efficiency, i. e. a strong forwardpropulsion per electric power supplied by the propulsion system, forexample through the power inlet. This may improve the efficiency of anelectric watercraft comprising the electrically driven propulsionsystem. In particular, a propeller coupling 106 p, a propeller shaft 106c or a propeller 104 of a surface drive has an optimum revolution speedsimilar to a revolution speed of an electric motor 102 such as an axialflux motor 102. Installing the electrically driven propulsion system 100as a surface drive therefore supports the use of a transmission 106 witha small gear ratio, which improves the energy efficiency and thus therange further.

The foregoing description should not be read as implying that anyparticular element, step, or function can be an essential or criticalelement that must be included in the claim scope. Also, none of theclaims can be intended to invoke 35 U.S.C. § 112(f) with respect to anyof the appended claims or claim elements unless the exact words “meansfor” or “step for” are explicitly used in the particular claim, followedby a participle phrase identifying a function. Use of terms such as (butnot limited to) “mechanism,” “module,” “device,” “unit,” “component,”“element,” “member,” “apparatus,” “machine,” “system,” “processor,”“processing device,” or “controller” within a claim can be understoodand intended to refer to structures known to those skilled in therelevant art, as further modified or enhanced by the features of theclaims themselves, and can be not intended to invoke 35 U.S.C. § 112(f).Even under the broadest reasonable interpretation, in light of thisparagraph of this specification, the claims are not intended to invoke35 U.S.C. § 112(f) absent the specific language described above.

The present disclosure may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Forexample, each of the new structures described herein, may be modified tosuit particular local variations or requirements while retaining theirbasic configurations or structural relationships with each other orwhile performing the same or similar functions described herein. Thepresent embodiments are therefore to be considered in all respects asillustrative and not restrictive. Accordingly, the scope of theinventions can be established by the appended claims rather than by theforegoing description. All changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein. Further, the individual elements of the claims are notwell-understood, routine, or conventional. Instead, the claims aredirected to the unconventional inventive concept described in thespecification.

LIST OF REFERENCE SIGNS

-   100 electrically driven propulsion system-   102 electric motors-   104 propeller-   106 transmission-   106 a motor shaft-   106 b gearbox-   106 c propeller shaft-   106 e encased section of transmission-   106 p propeller coupling-   106 x external section of transmission-   108 common waterproof housing-   108 a motor section-   108 b transmission section-   110 sealing face of the electrically driven propulsion system-   110 a through holes on the sealing face of the electrically driven    propulsion system-   112 rudder actuator-   114 b buckboard rudder-   114 s starboard rudder-   116 data line-   116 c data input connector-   118 pulse inverter-   120 power inlet-   122 heat exchanger-   124 primary side of the heat exchanger-   124 c primary coolant channel-   1240 primary coolant opening-   126 secondary side of the heat exchanger-   126 c secondary coolant channel-   1260 secondary coolant opening-   128 support element-   128 a support arm-   128 b support column-   130 offset along the vertical direction-   132 thrust bearing-   134 common tiller arm-   134 s starboard tiller arm-   136 portion of the encased section of the transmission outside the    watercraft-   138 motor upgrade space-   140 stator-   142 rotor-   144 radial section of propeller-   146 essentially flat section of propeller-   146 e outer edge of flat section of propeller-   β Angle between outer edge and radial direction-   γ Angle between outer edge and center line-   148 diameter of propeller-   150 pitch of propeller-   152 noise/vibration sensor-   154 signal line of noise/vibration sensor-   156 processor for analyzing signal of noise/vibration sensor-   158 longitudinal direction-   160 plane perpendicular to longitudinal direction-   162 second plane perpendicular to longitudinal direction-   164 thrust bearing-   166 force/propulsion along axial direction-   166′ transferred force/propulsion-   168 axial direction-   200 method for connecting the electrically driven propulsion system    to a hull with an opening-   202 hull, transom-   204 opening of hull, transom-   210 second side, outside-   212 seal for the sealing face of the electrically driven propulsion    system-   214 moving the motor section through the opening-   216 first side, inside-   218 fixing the electrically driven propulsion system to the hull,    transom-   218 a inserting bolts, pushing bolts through holes-   218 b screwing bolts into threaded holes-   220 through holes of hull, transom-   222 bolts for the threaded holes on the sealing face of the    electrically driven propulsion system-   230 providing the electrically driven propulsion system-   232 forming a waterproof connection-   302 connecting frame-   304 opening of the connecting frame-   304 a opening of first ring-shaped element-   304 b opening of second ring-shaped element-   306 first ring-shaped element-   308 second ring-shaped element-   310 first sealing face of the connecting frame-   312 seal for the first sealing face of the connecting frame-   316 threaded holes as first connecting means of the first    ring-shaped element-   318 through holes as a second connecting means of the second    ring-shaped element-   320 a through holes of first ring-shaped element-   320 b threaded holes of second ring-shaped element-   322 bolts for the threaded holes of the first ring-shaped element-   400 static water line-   400′ planing-speed water line-   402 lower edge of opening of hull, transom-   404 hull, watercraft for surface drive

What is claims is:
 1. An electrically driven propulsion system for awatercraft, the electrically driven propulsion system comprising: anelectric motor adapted to provide a mechanical power of at least 50 kW;a transmission comprising a rotary shaft; a pulse inverter electricallycoupled to the electric motor and adapted to provide an electricalsupply power of at least 50 kW to the electric motor; a thrust bearing;and a common waterproof housing; wherein the electric motor, the pulseinverter and an enclosed section of the transmission are arranged insidethe common waterproof housing; wherein an external section of thetransmission is arranged outside of the common waterproof housing;wherein the transmission is adapted to rotationally couple the externalsection of the transmission to the electric motor; and wherein thethrust bearing is mechanically coupled to the rotary shaft of saidtransmission and to the common waterproof housing and adapted totransfer a force applied to the transmission along an axial direction ofsaid rotary shaft to the common waterproof housing.
 2. The electricallydriven propulsion system according to claim 1, wherein the externalsection of the transmission comprises a propeller coupling adapted formounting a propeller thereto.
 3. The electrically driven propulsionsystem according to claim 2, wherein the watercraft comprises a hullwith an opening; and wherein the electrically driven propulsion systemis adapted to be connected as a whole to the hull with the opening, suchthat at least a section of the electric motor is arranged on a firstside of the opening and the propeller coupling and at least a portion ofthe common waterproof housing are arranged on a second side of theopening opposite to the first side, and such that a waterproofconnection forms between the common waterproof housing and the hull. 4.The electrically driven propulsion system according to claim 1, whereinthe electric motor is an axial flux motor.
 5. The electrically drivenpropulsion system according to claim 1, wherein the common waterproofhousing is adapted to provide a motor upgrade space for a motor powerupgrade component, and wherein the pulse inverter is adapted to providean electrical output power of at least two times the mechanical powerthat the electric motor is adapted to provide.
 6. The electricallydriven propulsion system according to claim 1, which further comprises asensor disposed within the common waterproof housing and adapted todetect a change in a sound or vibrational level of the electricallydriven propulsion system.
 7. The electrically driven propulsion systemaccording to claim 3, wherein the common waterproof housing comprises amotor section in which the electric motor is arranged; and wherein awidth of the portion of the common waterproof housing adapted to bearranged on the second side of the opening exceeds a width of the motorsection.
 8. The electrically driven propulsion system according to claim3, wherein the common waterproof housing comprises a ring-shaped sealface adapted to encircle the opening of the hull to provide thewaterproof connection.
 9. The electrically driven propulsion systemaccording to claim 2, wherein the transmission comprises a shaftcomprising the propeller coupling and an axis, and wherein anorientation of the axis of the shaft is static.
 10. The electricallydriven propulsion system according to claim 3, further comprising a heatexchanger disposed within the common waterproof housing, wherein aprimary side of the heat exchanger comprises at least one primarycoolant opening adapted to be arranged on the second side of theopening, and wherein a secondary side of the heat exchanger comprises atleast one secondary coolant opening adapted to be disposed proximate thefirst side of the opening.
 11. The electrically driven propulsion systemaccording to claim 1, which further comprises a rudder actuator, whereinat least a section of the rudder actuator is disposed within the commonwaterproof housing.
 12. A connecting frame for connecting a propulsionsystem to a hull with an opening, wherein the connecting framecomprises: a first ring-shaped element comprising a first opening, firstconnecting elements, and through holes; a second ring-shaped elementcomprising a second opening; second connecting elements, wherein thefirst connecting elements and the second connecting elements comprise afirst common arrangement; and detachable connection elements adapted tocouple to fixing means of the propulsion system; a first sealing facearranged on the first ring-shaped element and encircling the firstopening; and a second sealing face arranged on the first ring-shapedelement opposite to the first sealing face and encircling the firstopening; wherein the first ring-shaped element and second ring-shapedelement are adapted to be connected using the first connecting elementsand the second connecting elements and with a relative orientationdefined by the first common arrangement; and wherein, according to therelative orientation: the first opening overlaps with the second openingto form an opening of the connecting frame; the through holes coincidewith the detachable connection elements; and the first sealing face isarranged between the connected first ring-shaped element and secondring-shaped element and adapted to provide a waterproof connectionbetween the connecting frame and the hull with the opening.
 13. Aconnecting system, comprising: a connecting frame configured to couple apropulsion system to a hull with an opening, wherein the connectingframe comprises: a first ring-shaped element comprising a first opening,first connecting elements, and through holes; a second ring-shapedelement comprising a second opening; second connecting elements, whereinthe first connecting elements and the second connecting elementscomprise a first common arrangement; and detachable connection elementsadapted to couple to fixing means of the propulsion system; a firstsealing face arranged on the first ring-shaped element and encirclingthe first opening; and a second sealing face arranged on the firstring-shaped element opposite to the first sealing face and encirclingthe first opening; wherein the first ring-shaped element and secondring-shaped element are adapted to be connected using the firstconnecting elements and the second connecting elements and with arelative orientation defined by the first common arrangement; and asupport element adapted to mechanically support the propulsion systemvia a support arm.
 14. The connecting system according to claim 13,wherein the support element is adapted to be coupled to the connectingframe such that the support arm extends away from the connecting frame.15. The connecting system according to claim 13, wherein, according tothe relative orientation: the first opening overlaps with the secondopening to form an opening of the connecting frame; the through holescoincide with the detachable connection elements; and the first sealingface is arranged between the connected first ring-shaped element andsecond ring-shaped element and adapted to provide a waterproofconnection between the connecting frame and the hull with the opening.16. A method for connecting an electrically driven propulsion system asa whole to a hull with an opening, wherein the electrically drivenpropulsion system comprises: an electric motor adapted to provide amechanical power; a transmission functionally coupled to the electricmotor, the transmission comprising a propeller coupling adapted formounting a propeller; and a common waterproof housing, wherein theelectric motor and an enclosed section of the transmission are arrangedinside the common waterproof housing, wherein the propeller coupling isarranged outside the common waterproof housing, wherein the transmissionis adapted to rotationally couple the propeller coupling to the electricmotor, and wherein the common waterproof housing comprises a motorsection in which the electric motor is arranged; the method comprising:providing the electrically driven propulsion system as a whole on asecond side of the opening of the hull; moving at least a section of themotor section through the opening to a first side of the openingopposite to the second side, such that at least a portion of the commonwaterproof housing remains on the second side; and fixing theelectrically driven propulsion system to the hull with the opening; andforming a waterproof connection between the hull with the opening andthe common waterproof housing.
 17. The method according to claim 16,wherein the fixing the electrically driven propulsion system to the hullwith the opening comprises fixing the electrically driven propulsionsystem as a surface drive to the hull with the opening.
 18. The methodaccording to claim 16, wherein the electric motor provides a mechanicalpower of at least 50 kW.
 19. The method according to claim 16, whereinthe at least a section of the motor section is moved through the openingwhile keeping the electrically driven propulsion system assembled as awhole and while keeping the propeller coupling on the second side. 20.The method according to claim 16, wherein the at least a section of themotor section is moved through the opening while keeping the propellercoupling on the second side.